ByYuri Kageyama, Associated PressMay 5, 2012

Tokyo — Thousands of Japanese marched to celebrate the switching off of the last of their nation's 50 nuclear reactors Saturday, waving banners shaped as giant fish that have become a potent anti-nuclear symbol.

Japan will be without electricity from nuclear power for the first time in four decades when the reactor at Tomari nuclear plant on the northern island of Hokkaido goes offline for routine maintenance.

After last year's March 11 quake and tsunami set off meltdowns at the Fukushima Dai-ichi plant, no reactor halted for checkups has been restarted amid public worries about the safety of nuclear technology.

"Today is a historical day," Masashi Ishikawa shouted to a crowd gathered at a Tokyo park, some holding traditional "koinobori" carp-shaped banners for Children's Day that have become a symbol of the anti-nuclear movement.

"There are so many nuclear plants, but not a single one will be up and running today, and that's because of our efforts," Ishikawa said.

The activists said it is fitting that the day Japan is stopping nuclear power coincides with Children's Day because of their concerns about protecting children from radiation, which Fukushima Dai-ichi is still spewing into the air and water.

Government eager to restart reactors

The government has been eager to restart nuclear reactors, warning about blackouts and rising carbon emissions as Japan is forced to turn to oil and gas for energy.

Japan now requires reactors to pass new tests to withstand quakes and tsunami and to gain local residents' approval before restarting.

The response from people living near nuclear plants has been mixed, with some wanting them back in operation because of jobs, subsidies and other benefits to the local economy.

Major protests, like the one Saturday, have been generally limited to urban areas like Tokyo, which had received electricity from faraway nuclear plants, including Fukushima Dai-ichi.

One third of Japanese power

Before the nuclear crisis, Japan relied on nuclear power for a third of its electricity.

The crowd at the anti-nuclear rally, estimated at 5,500 by organizers, shrugged off government warnings about a power shortage. If anything, they said, with the reactors going offline one by one, it was clear the nation didn't really need nuclear power.

Whether Japan will suffer a sharp power crunch is still unclear.

Electricity shortages are expected only at peak periods, such as the middle of the day in hot weather, and critics of nuclear power say proponents are exaggerating the consequences to win public approval to restart reactors.

Hokkaido Electric Power Co. spokesman Kohei Ofusa said Saturday's shutdown was proceeding as planned. Power generation was gradually being reduced, with all operations expected to end at 11 p.m. (1400 GMT), he said.

Yoko Kataoka, a retired baker who was dancing to the music at the rally waving a small paper Koinobori, said she was happy the reactor was being turned off.

"Let's leave an Earth where our children and grandchildren can all play without worries," she said, wearing a shirt that had, "No thank you, nukes," handwritten on the back.